Bob,
I can understand preferring to fly than trailer.
Another factor is what your performance expectations are. The S6 has a claimed L/D of 34/1, so depending on how strong conditions are, you may need to run the motor occasionally to stay up with the slippery ships. Some pilots, including me, consider having to do an engine start as somehow "losing". Hawks and eagles, on the other hand, seem pretty much indifferent to the need to flap now and then.
The Stemme S10, claimed L/D is 50, but really more like 46 to 47. The S10's polar does have a nice sweet spot at 90 knots though.
Haven't flown the S6, so don't know if they are being "optimistic" on their performance claims.